Background

Although approved for commercialisation in a number of countries since the 1990s, the potential environmental, human/animal health, and socio-economic impacts of genetically modified (GM) crops are still widely debated. One category of human health impacts (designated in this review as non-food health impacts) focuses on indirect effects of GM crop cultivation; amongst which the most prominent are health benefits via: (1) reduced use of pesticides, and (2) an increase in income. Both of these pathways have raised a lot of interest in the developing world, especially in areas experiencing high rates of pesticide poisonings and low agricultural incomes. However, evidence to support such benefits has been relatively scarce in comparison to that of GM food health impacts. Non-food health impacts of GM crop cultivation on farmers deserve more attention, not just because of an apparent knowledge gap, but also because of, potential economic and environmental implications, involving for example CO ₂ emissions, underground water contamination and improved sanitation.

Methods/Design

The primary research question was: What are the non-food impacts of GM crop cultivation on farmers’ health? To address this primary question, the study focused on two related secondary questions: (1) Does the cultivation of GM crops result in a lower number of pesticide-related poisonings as compared to the cultivation of their non-GM counterparts?, and; (2) Does the cultivation of GM crops allow for higher financial resources to be used by farmers to improve the health status of themselves and their family, as compared to the cultivation of the non-GM counterpart? The extent to which information relevant to the two secondary questions was freely-available was also evaluated. The search and assessment methodologies were adapted following experience gained during a scoping exercise, and followed the published protocol.

Results

The 20 databases and 10 reviews searched returned 4,870 hits, with 19 identified as relevant for data extraction. It was apparent that the 19 articles were derived from only 9 original studies, of which 7 were relevant to the first research question, whilst the remaining 2 were relevant to the second question. The studies showed both an overall decrease in the amount of pesticides applied and an increase in household income from GM crop cultivation as compared to the cultivation of the non-GM counterpart.

Conclusion

In the absence of additional confounding variables or statistical analyses to support these findings, any correlation from these studies should be considered circumstantial at best. Even though the cultivation of GM crops appears to increase household income, evidence to demonstrate that farmers invested this extra income in improving their health remained inconclusive. Further research is therefore needed to clarify the possible correlation between GM crop cultivation and (1) pesticide poisonings, and (2) overall health improvements. Future impact evaluations should include: both written records and surveys; statistical correlations between independent and dependent variables; testing the characteristics of the samples for statistical significance to indicate their representativeness of a particular population, and; increasing the importance of confounding variables in research design (by identifying specific variables and selecting sample and control groups accordingly).